AI companies for years have promised that smarter models would be worth the staggering cost to build them. Anthropic on Wednesday made that case in cash.The company presented eye-popping financials to investors, saying it was cash flow positive in the third quarter, with revenue surging nearly 50% to $16.8 billion compared to the April-to-June period.Why it matters: As Wall Street broadly spent the day fearing an AI bubble, Anthropic offered what investors have been desperate to see: evidence that frontier AI can be a sustainable business.State of play: As concerns about the AI trade pushed the S&P 500 down by more than 1% for the first time in 53 sessions, Anthropic showed off a balance sheet that offered the promise of profitable AI, sources told Axios.Zoom in: Consider just one of the stats reported by Anthropic: the company is cash flow positive even as some of the world's most profitable companies are struggling to keep their AI spending in check.For context, Google parent Alphabet, long a money-printing machine, turned free cash flow negative in its second quarter as AI infrastructure investment soared.Investing gurus — especially those focused on the frothiness of companies relative to their underlying value — have long...